Forms or molds are widely used in the construction of cast-in-place concrete building foundation wall slabs. Concrete is preferred as a construction material for several reasons. For one, concrete is economical because the basic constituent materials, cement, sand, aggregate, and water, are usually available locally, so that local sources of both labor and materials can be used in a construction project. Concrete is preferred as a foundation material because of its excellent compression strength; however concrete is also a brittle composite material which has relatively poor tensile strength, so that a tensile stress that exceeds such tensile strength caused by factors such as an applied load, shrinkage, or temperature changes can cause concrete cracking and possible failure. Fortunately, reinforcing materials including steel bars (rebar) and/or other metal wire enforcement or tie materials if formed as part of a concrete slab greatly increase the lateral or tensile strength of the slab, and help absorb and distribute tension due to expansion and contraction of the concrete. As a result, if provided with waterproofing and other proper protection from climatic and environmental elements, building foundations made of reinforced concrete are sturdy and long-lasting.
Use of forms to mold concrete perimeter foundation walls into desired structural shapes is prescriptive in most construction code books. Concrete forms are conventionally built on-site out of pairs of plywood sheets which are aligned in a spaced-apart opposing relationship and are supported by wood beams or other support means so as to define cavities or voids in which the concrete foundation is poured. Various prefabricated form systems made of alternative materials such as steel, aluminum, and plastic are also available, which systems may be modular and include their own support or bracket systems. Once the concrete has been poured, which is usually preceded by the placement of a reinforcing steel material in the form cavity, and has completely set up, conventional forms are removed, leaving a foundation wall in the desired shape having essentially smooth outer and inner surfaces. In some newer systems, however, the formwork stays in place after the concrete has set up, either to provide additional reinforcement or some other purpose such as acting as an insulating barrier. It is also known to place other components in a concrete form before the concrete is poured, such as pipe inserts to create apertures for conduit passing through the wall, and liners for insulation purposes or to provide an architectural textured surface on the finished wall.
One shortcoming of conventional poured concrete residential wall construction is that it is not an inexpensive process which requires substantial quantities of construction materials as well as significant on-site skilled labor to excavate and ready the site for building, erecting the forms, pouring the concrete and allowing for curing, removing the forms, and other operations, all of which add time and expense to a building project. Conventional residential construction also typically requires a footer or footing to be formed under the foundation to transmit the load from the walls into the underlying soil. Typical residential homes require a sixteen or twenty inch wide footer that is six to sixteen inches in depth, although this it will be understood can vary depending upon the size and type of home construction, the bearing capacity of the soil, and local building codes. Preparing for, pouring, and allowing the footer to cure sufficiently before a foundation wall is poured adds several days and significant cost to a residential home construction. In addition, since concrete is permeable to water, a water-proof coating usually must be applied to the wall. Concrete foundation walls should also be insulated to prevent loss of heat through the wall to the soil or open air by conduction.
It is desirable therefore to reduce the overall construction time, labor, and cost of residential and light construction. Many attempts to lower construction costs are related to replacing on-site labor with generally less expensive factory labor and precast or prefabricated systems. However, prefabricated buildings have their own costs including transportation costs. The following references are exemplary of existing alternative wall and floor building and foundation construction applications and systems.
U.S. Pat. No. 5,803,964 issued to Scarborough discloses the use of an expanded polymeric foam such as expanded polystyrene (EPS) in building construction applications including formation of structural sections and building foundations. The Scarborough system preferably forms complete concrete structures made of EPS, which material is covered by a layer of sprayed concrete that binds to the EPS. Additional concrete or rod reinforcing is provided where required, and the outer surface is sealed by a sprayed polymer resin.
U.S. Pat. No. 6,076,320 issued to Butler discloses a method of constructing a cast-in-place perimeter wall foundation comprised of corrugated steel panels in which the bottom edges of the panels are cast in a concrete footing. In one embodiment the Butler system is finished on the exterior by applying rigid foam panels to the steel structure and then stuccoing over the foam. The Butler foundation system is designed for modular construction applications such as mobile homes.
U.S. Pat. No. 6,119,432 issued to Niemann discloses a cast-in-place foundation system in which foam panels are used as forms to create channels for the poured concrete, and which foam panels are left in place after the concrete cures to form a composite structure. The Niemann panels are not reusable, and the system requires additional parging on the exterior panel as a finish.
U.S. Pat. No. 6,272,749 issued to Boeshart et al. discloses a form system for insulated concrete decks. The Boeshart system is a horizontal application in which concrete is poured on top of a plurality of interconnected expanded polystyrene form panels having a channel cut on the opposite side from the concrete receiving surface in which an insert having engaged structural members is housed. Thus, the Boeshart et al. system is not used to form cast-in-place vertical walls, and using the decks as wall panels would comprise a precast wall system requiring heavy equipment to move and set the panels.
U.S. Pat. No. 6,739,102 issued to Roy, Sr. discloses a cast-in-place trench foundation wall wherein the forms used to create a cavity to hold poured concrete are made of extruded foam insulation, preferably extruded polystyrene, and are backfilled against on both sides. The panels are maintained in place after the poured concrete has hardened. Roy, Sr. does not provide a form insert and does not alter the conventional concrete foundation wall. In addition, this invention is not meant for unbalanced fill situations which are found in crawlspaces and basements exterior surface, still requires a finish above grade such as a stucco finish.
U.S. Pat. No. 6,817,150 issued to Boeshart discloses another horizontal roof and floor deck system which is similar to the Boeshart et al. '749 patent but additionally comprises a means for increasing the thickness of the polystyrene panels such that the slots filled with concrete between the panels are thicker. As in the '749 patent, the system is poured horizontal not vertical would require heavy equipment to move and place the walls if they were used for a wall application.
U.S. Pat. No. 7,185,467 issued Marty teaches an integral insulative foam and concrete panel cast-in-place forming system designed to replace and act as post and beam construction just using concrete instead of wood and steel. Marty therefore is not a foundation system but a slab on grade construction technique.
U.S. Pat. No. 7,810,293 issued to Gibbar et al. discloses a precast as opposed to a cast-in-place foundation system that is poured flat and requires heavy equipment to move and place the forms.
U.S. Patent Application Publication US2008/0184650 filed by Fischer discloses a form of insulated concrete block in which a foam layer is provided on the inside and outside face but also includes a foam middle layer, which blocks are stacked one on top of another and side by side to create a wall, after which the blocks are filled with concrete. A stucco coating is then applied as an exterior finish.
U.S. Patent Application Publication 2008/0216445 filed by Langer utilizes a decorative finishing product such as drywall, brick, decorative stone, and ceramic tile on the interior and exterior of a wall to take the place of a form, whereby concrete is poured into the void between the products to form either precast or cast-in-place structures so that all the products are bound together. The Langer system is a monolithic building assembly more suited for above ground applications and multi-story building, and requires special products that can be exposed to uncured concrete to create the interior and exterior assemblies.
While these other building systems and methods are presumably suited for their particular intended purposes, there remains a need in the construction industry for a cast-in-place foundation wall construction that is particularly useful in constructing residential, light commercial, and light industrial buildings, that significantly reduces the amount of on-site labor, time, and expense of a building project, and where the resulting foundation wall is strong enough to bear both the compressive and lateral loads typically imposed on concrete walls in such building structures and applications. Prior art walls that attempt to replicate similar advantages are primarily precast walls which are formed flat within a mold and after the concrete cures require heavy equipment including tractor trailers for shipping to the construction site and/or cranes to lift the walls into place. While reducing material, this technique requires a large expense to move and set the walls. Other cast-in-place systems use flat sheets of foam on both sides of the concrete as forms.